This invention relates to synchronous electric machines, and more particularly, to a novel circuit for generating a rotating field in a synchronous, three phase electric machine which serves as driving motor for a flywheel starter for the internal combustion engine of a vehicle.
An automobile whose flywheel is integrated with an electric motor serving as a generator as well as a starter is known, e.g., from commonly owned German Offenlegungsschrift No. 29 25 675 (corresponding to U.S. application Ser. No. 159,836, filed June 16, 1980). Arrangements of this kind offer a special advantage in that in certain operating states, in particular, when the internal combustion engine does not propel the automobile, the engine, following uncoupling from the flywheel, is stopped and can again be started by use of the kinetic energy stored in the rotating flywheel. Such an arrangement, in which the engine may be selectively stopped and rapidly restarted, offers special energy savings.
The structure of the automobile drive of this kind is disclosed in the aforementioned U.S. application Ser. No. 159,836, which is incorporated herein by reference.
The field windings of a synchronous, three phase motor must be supplied by a rotating field which rotates in proper phase with the rotor of the synchronous motor, such that the rotor is carried along by the rotating field. The various field windings, generally three or six windings, must be supplied during identical current flow angles which must be precisely adhered to. Furthermore, it has been found that the pole wheel angle, i.e., the angle between the rotating field and the rotor of the synchronous motor, must be varied, e.g., to achieve optimum acceleration of the synchronous motor with the coupled internal combustion engine flywheel.